Methods of manufacturing electrodes for cathode ray tubes



May 6, 1969 J. H. JOHNSON 3,442,008

METHODS OF MANUFACTURiNG ELECTRODES FOR CATHODE RAY TUBES Original FiledDec. 30, 1965 PRIOR ART FIG] INVENTOR 26 JAY H. JOHNSON ATTORNEYS UnitedStates Patent 3,442,008 METHODS OF MANUFACTURING ELECTRODES FOR CATHODERAY TUBES Jay H. Johnson, Owensboro, Ky., assignor to KentuckyElectronics, Inc., Owensboro, Ky., a corporation of Delaware ApplicationDec. 30, 1965, Ser. No. 517,679, now Patent No. 3,381,156, dated Apr.30, 1968, which is a continuation-in-part of applications Ser. No.221,600, Sept. 5, 1962, and Ser. No. 221,601, Sept. 5, 1962. Divided andthis application Jan. 8, 1968, Ser. No. 696,230

Int. Cl. H01j 9/02 US. Cl. 29-477 7 Claims ABSTRACT OF THE DISCLOSUREThe method of forming cathode ray tube electrodes by rolling a thin flatblank into cylindrical form with two ends abutting at a seam isdisclosed. The seam may be notched or welded to interlock and the blankmay have its edges rounded to prevent possibility of burrs and resultingcorona discharge. The latter may be accomplished by forming the blank ofa wire which is rolled and flattened to a constant width blank withrounded edges.

This application is a divisional application from the co-pendingapplication of Jay H. Johnson, filed Dec. 30, 1965, Ser. No. 517,679,now Patent No. 3,381,156 for Manufacture of Electrodes for Cathode RayTube, which in turn is a continuation-in-part of applications Ser. No.221,600, now Patent No. 3,231,959 and No. 221,601, filed Sept. 5, 1962HOW abandoned.

This invention relates to methods of manufacturing parts for electrontubes and, more particularly, to forming cylindrical electrodes forelectron guns'in cathode ray tubes.

In the prior art, various methods were employed to fabricate annularfocusing anodes for electron guns which have been conventionally formedheretofore of seamless cylindrical stock. For example, one such methodof forming a cylindrical electrode such as the focusing anode is to forma cup from strip material on an eyelet machine by puncturing the stripbefore forming it in a progressive die-drawing operation. Next, theupper flange of the cup is trimmed to proper dimension and then thebottom of the cup is pierced to complete the annular ring. When theupper flange is trimmed, an outer lip is produced. The piercing of theend Wall of the cup leaves a lip on the lower flange or opposite flangeof the anode. These irregularities tend to cause an out of roundnesswhich disturbs proper beam-shaping operation, for example, in the caseof a cylindrical focus anode, because they produce irregularities in theelectrostatic field surrounding the anode so that the field along theaxis of the cylinder is irregular. Furthermore, any sharp edges orprojections can cause corona since some of the electrodes are operatedat very high potential.

In addition to other defects of electrodes made by prior art methodswhich produce difliculty in meeting roundness and dimensionaltolerances, a simpler, more eflicient manufacturing technique isdesirable to reduce the possibility of rejects which increases when moreprocessing steps are introduced. Also, a method of manufacturingelectrodes is desirable which does not involve the use of tools and diesin formation of critical tolerance dimensions such as roundness whichare subject to significant wear and deformation by abrasive actionagainst the parts when they are drawn or reshaped.

Accordingly, it is an object of this invention to provide an improvedmethod for constructing electrodes for an electron tube.

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It is another object of this invention to provide an improved method forconstructing an annular ring electrode for an electron gun.

Briefly, in accordance with aspects of this invention, I provide acylindrcial electrode member with a seam extending along the directionof beam travel, which I find does not interfere with processing of thebeam, and thus obviates the disadvantages of the .prior art methods ofcylindrical electrode construction by forming a flat blank the desiredlength, rolling the blank into a cylinder and joining it at the ends byany convenient means such as by an interlocking arrangement of teeth andnotches. When the blank is formed by rolling from a round wire or rod,the edges are rounded without further processing and undesirable li-pstructure on the edge of the annular ring produced by the prior artmethods is eliminated.

These and various other objects and features of the invention are setforth in the detailed description of the invention with reference to theaccompanying drawings in which:

FIGURE 1 is a view in section of an annular anode produced by the abovedescribed prior art method;

FIGURE 2 is a view in elevation of a rod employed in this novel method;

FIGURE 3 is a blank formed from the rod of FIG- URE 2 and includinginterlock structure for joining the ends of the blank; 0

FIGURE 4 is a side view of an annular ring formed from a flat blank suchas shown in FIGURE 3; and

FIGURES 5 through 8 show typical tools for forming the cylinder from aflat blank in a typical operational sequence.

Referring now to FIGURE 1, there is depicted a view in section of anannular ring 10 formed by the prior art method described above. Thisring 10 has an outer lip 12 on one edge and an inner lip 14 on theopposite edge. The lip '12 is formed when this edge is trimmed. The lip14 is formed when the end wall of the cup is pierced to define anannular ring. In each instance, the flange must be subsequently machinedto a very close tolerance. In addition to the elimination of the lips 12and 14, the internal and external diameters of focus anodes must be heldwithin close tolerances for the entire length of the ring and it hasbeen difficult to maintain tolerances of -.001 on both internal andexternal diameters for the entire length of the ring under the priorart.

The novel focus ring according to this invention remains within anout-of-round tolerance of :.001 both before and after firing(heat-treating to remove impurities and gas from the ring prior toassembly of the cathode ray tube) even when fired in a bulk container.The prior art focus rings are work-hardened and subjected to stresses bythe repeated drawing and machining process. Unless they are individuallystacked for firing, the hardening and stresses tend to be relievedunevenly and cause the rings to become misshapen. They cannot,therefore, be fired as simply in bulk to meet the exacting roundnesstolerances imposed upon electrodes for electron guns.

Referring now to FIGURE 2, there is depicted a rod or wire 18 which isemployed in this novel to produce an annular anode. The first step inthis method is to roll and flatten a wire of proper diameter to producethe desired round edges (28, 30 FIGURE 4) while obtaining the desiredflat blank having a typical width such as .500 inch ':.005 inch andthickness of .025 inch. After the desired width is obtained, notches orgrooves 20 preferably are cut in one end of the blank 22, whileinterlock members or tongues 24 are cut on the opposite end of theblank. The blank 22 is now rolled over a suitable form, as laterdecribed to form annular ring 26 shown in FIGURE 3 4, with theinterlocks 24 engaged in the notches 20 to secure the ends of the blankto each other thereby preventing any change of circumferential dimensionduring firing or use in an electron gun. The beam passes through thiselectrode in a general direction substantially the same as that of theseam.

Alternatively, the blank may be secured together by other structuralmethods such as abutting together noninterlocking tongues and groovesfor securing by spot welding together at the overlapped seams in thesame manner as shown at 38 in FIGURE 4. It is noted, however, that thepreferable construction of interlock members and notches prevents anymisshaping of the cylindrical tolerances either by expansion orcontraction due to heat expansion or other stresses over a more stablesurface area than reliance upon the spot weld position alone. Thus, ininterlocked structure of FIGURE 4 the spot weld serves to retain theinterlock members against radial changes of the end portions to preventany change in roundness during handling or assembly of the electrode anddoes not need to bear the greater circumferential stresses that may beimposed during heating of the electrode and its mounts in the tube orduring processing.

With this novel method, both internal and external diameters of theannular ring 26 of .625 inch inner diameter easily can be held withintolerances of plus and minus .001 inch, which tolerances are not readilyachieved by prior art methods. Further, because the blank 22 was rolledfrom a round wire 18, the edges 28 and 30 of the blank are round andthus, do not require subsequent machining to eliminate irregularitieswhich might cause corona or out-of-roundness.

The fiat electrode blank 22 is rolled over a cylindrical mandrel 40 bysequential movement of die members 41, 42, 43, and 44 in the mannerillustrated in FIGURES through 8. Note in FIGURE 7 that die 42 isinserted before die 43 to permit the interlock members 24 to overlap thetop of the rolled cylindrical blank 26 of FIG- URE 8, where they arepressed into fit by die member 44. Note that little abrasive actionagainst the blank 22 is introduced by the rolling action. Thus, thepresent method causes little wear of the dies or mandrel, asdistinguished over prior art methods of deep drawing or dieforming, andthere results a manufacturing process which produces electrodes heldmore closely within tolerances over long periods of time.

Therefore, this invention has provided a new electrode configuration forcylindrical electron gun electrodes which have a seam along the regionof abuttment of the ends of a single flat metal blank wrapped intocylindrical form, together with methods of forming the electrode.

Contrary to possible expectation, the seam produced by the abutting endsof the blank does not materially affect the action of the electrode uponthe beam, since there is no difference of potential on opposite sides ofthe seam to serve as a focusing member, it is generally oriented alongthe cylinder in the direction of beam travel and there is very littlechange of radial dimension of the cylinder to eifect the beam passingthrough the cylindrical electrode by changing the field configuration atthe position of the beam. Thus, it has been found that the seamedcylinder is an entirely satisfactory replacement for the prior art solidtubular equivalents.

Having therefore particularly described the advantages and nature of theinvention and its method of operation, those features believeddescriptive of the scope and spirit of the invention are set forth withparticularity in the appended claims.

What is claimed is:

1. The method of processing a metal blank to form 7 distortion orcorona; comprising in combination the steps of producing a thin fiatblank of substantially constant width equal to the axial length of theelectrode, rolling the blank over its faces to provide a constantthickness thereby to distribute stresses to substantially eliminatemisshaping when subjected to firing and thermal stress, processing twoends of the blank to interfit at a single seam, rolling the blank toform an annular ring with an internal cylindrical surface of constantdiameter over the entire inner surface for establishing a uniformelectric field for processing the electron beam passing through thecylinder with the ends of the blank meeting at the seam in a directiongenerally parallel with the axis of the cylinder and along the path ofthe electron beam through the electrode, securing the ends of the blanktogether at the seam to prevent circumferential movement at the seamwhich might tend to change said constant diameter in the vicinity of theseam when subjected to thermal or physical stresses encountered within acathode ray tube, and thereafter firing a plurality of said electrodesin bulk.

2. The method defined in claim 1, including the additional step ofprocessing the blank to round the edges.

3. The method of manufacturing a cylindrical electrode for passing anelectron beam axially therethrough in an electron gun having preciseroundness and surface tolerances, comprising the steps of forming astrip of rectangular cross-sectioned flat blank of a Width equal to thelength of the electrode along the beam path and of a length equal to thecircumference of the electrode to be formed, rolling the blank about amandrel to form a cylinder, with ends of the blank abutting along a seamto extend generally in the direction of beam travel through theelectrode to form a cylindrical electron gun electrode member with asubstantially constant internal diameter for the entire length of theelectrode, securing the ends of the blank together to establish a stablecircumferential dimension and firing a plurality of electrodes so formedin bulk after being formed.

4. The method of claim 3, wherein the step of cutting the blank includesthe formation of at least one tongue at the end of the blank and atleast one groove on the opposite end of the blank whereby the tongue andgroove are engaged during the rolling step to connect the ends of theblank.

5'. The method of claim 4, wherein the step of cutting the blankincludes the shaping of the tongue and groove to interlock when theblank is rolled about the mandrel to thereby constitute the step ofsecuring the ends of the blank together.

6. The method of claim 3, comprising the additional step of spot weldingthe two ends of the blank together along the seam.

7. The method of claim 3, wherein the flat blank is formed by the stepsof rolling a rod member to thereby produce rounded edges on the blankwithout further processing steps.

References Cited JOHN F. CAMPBELL, Primary Examiner. J. L. CLINE,Assistant Examiner.

U.S. Cl. X.R. 2925.18, 521

